Lamb¿s lettuce mineral content in floating system

In recent times lamb's lettuce become a very interesting leafy vegetables to consumers because of its rich mineral and chemical composition. Due to a market demand for this valuable leafy vegetable throughout year, it is necessary to research other production technologies (such as floating system) beside conventional one. The aim of this research was to determine the influence of two different nutrient solutions on yield, dry matter, mineral and nitrate content of lamb's lettuce. The experiment was laid out according to the randomized block scheme with three replications in floating hydroponic system in unheated greenhouse. In the first pool nutrient solution was prepared according to Pimpini and in the second pool according to Johnson with a smaller concentration of potassium nitrate. Sowing of lamb's lettuce, cultivar 'Juwabel' was conducted on March 17 in polystyrene trays, filled with inert substrate. Nutrient solution prepared according to Johnson resulted with higher values of yield (1.26 kg m^-2), dry matter (12.95%), phosphorus [47.92 mg 100 g^-1 fresh weight (fw)], magnesium (53.1 mg 100 g^-1 fw) and calcium (116.6 mg 100 g^-1 fw). Also, smaller values of potentially harmful nitrate were measured (1425 mg kg^-1 NO₃ fw) compared to lamb's lettuce grown in Pimpini's nutrient solution (1881 mg kg^-1 NO₃ fw). Due to higher yield, dry matter and concentrations of the most observed minerals as well as smaller amounts of nitrate, nutrient solution according to Johnson can be proposed for growing of lamb's lettuce in floating system.